Possible fungus on Chinese elm and Prunus mume foliage

[zeejet]

I recently noticed that my Chinese elm has started dropping leaves after a quick spring burst of growth. The dead foliage looks like it's starting to yellow and has black splotches.

I suspect black spot fungus but I've seen it presented in two ways from photos online - either the fungus looks like it's growing on the surface of the leaf, or it looks to be developing within the leaf (like in my case). Can it be both?

I was also considering a trunk chop on this tree before this happened. Something tells me I should wait and try to heal the tree first, but the trunk chop would also remove a lot of the infected foliage. What should I do?

Additionally, I bought a cutting grown starter Prunus mume hybrid (mother tree was from a WB Clarke seedling that was open pollinated - sold by Brent Walston at Evergreen Gardenworks as Prunus mume x). It arrived with swiss cheese holes in a lot of the foliage already and recently developed these rust spots on healthy foliage as well.

Again, I'm speculating that this is rust spot fungus, but not sure as I'm still only in my first year of growing bonsai and this is these are the first obvious signs of potential disease I've ever encountered.

I already sprayed both of these trees with Bio-Advanced (Bayer) 3-in-1 pesticide, but that didn't seem to prevent these trees from being infected.

Any advice would be greatly appreciated.

 

[RODERLO]

In terms of the Chinese elm there is one thing you need to consider:
Did the tree lose all its leaves during winter? They can be semi evergreen when kept in warmer temps/inside the house. In that case, it will drop last years leaves while new spring growth is emerging.
This is nothing to be alarmed about.
Dead leaves on my elm also look like that sometimes (with those black spots) but I don't have fungal issues.

It would be very helpful to have a picture of the tree itself.
I would hold off on the trunk chop. That's a major move in a not ideal part of the year.

 

[zeejet]

In terms of the Chinese elm there is one thing you need to consider:
Did the tree lose all its leaves during winter? They can be semi evergreen when kept in warmer temps/inside the house. In that case, it will drop last years leaves while new spring growth is emerging.
This is nothing to be alarmed about.
Dead leaves on my elm also look like that sometimes (with those black spots) but I don't have fungal issues.

It would be very helpful to have a picture of the tree itself.
I would hold off on the trunk chop. That's a major move in a not ideal part of the year.

As you'll see the leaf drop isn't all old growth - a lot of the new growth that has hardened off is also dropping. I was losing around 5-10 leaves a day (checking every morning) for about a week now but I will say that it's slowing down (1-2 leaves this morning). It does have Daconil and BioAdvanced 3-in-1 applied (systemic fungicides).

I really hope this is just a seasonal change and not blackspot.

 

[rockm]

As you'll see the leaf drop isn't all old growth - a lot of the new growth that has hardened off is also dropping. I was losing around 5-10 leaves a day (checking every morning) for about a week now but I will say that it's slowing down (1-2 leaves this morning). It does have Daconil and BioAdvanced 3-in-1 applied (systemic fungicides).

I really hope this is just a seasonal change and not blackspot.

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This is hardly seasonal changes. Leaves drop because of shortening daylength in the fall. In spring, days are lengthening--there is no signal for the tree to drop leaves at this point--particularly on newer leaves. Probably black spot.

 

[badatusernames]

For the mume, remove any impacted leaves - looks like early shothole blight

I’ve found mine to be rather prone to it.

 

[B-Trees]

For the mume, remove any impacted leaves - looks like early shothole blight

I’ve found mine to be rather prone to it.

I'll second shot hole blight. I haven't had it yet but as a mume grower starting out it's on my radar.

Fixed copper spray in the fall seems to be the recommendation, as well as removing impacted leaves. until then:
1. watch your watering - this fungal pathogen likes wet roots and wet leaves. try keeping the leaves dry when you water and don't keep the roots too wet
2. build your tree's immune response (with compost) - this is kinda imo/ ymmv but I've had a lot of success using active garden compost/ aerated compost tea on my prunus mumes (happy to share more details if you're interested)

 

[zeejet]

2. build your tree's immune response (with compost) - this is kinda imo/ ymmv but I've had a lot of success using active garden compost/ aerated compost tea on my prunus mumes (happy to share more details if you're interested)

I've never come across this concept of building immune system for trees - would love to hear more.

 

[Kanorin]

As you'll see the leaf drop isn't all old growth - a lot of the new growth that has hardened off is also dropping. I was losing around 5-10 leaves a day (checking every morning) for about a week now but I will say that it's slowing down (1-2 leaves this morning). It does have Daconil and BioAdvanced 3-in-1 applied (systemic fungicides).

I really hope this is just a seasonal change and not blackspot.

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In my experience, Chinese elms tend to drop their leaves when treated with Bayer or bio advanced 3 in 1 systemic. I’m not sure which component does it. In any case, they usually bounce back.

 

[zeejet]

The shot-hole blgiht continues to spread despite removing all leaves that were affected. Same with the black spot on the elm although leaf drop and yellowing have slowed noticeably. Gonna follow up this weekend with copper and then manzoceb in another two weeks if this continues.

 

[Kanorin]

Another tip to help prevent it in the future - don't water the foliage when you water your chinese elms. Obviously the rain is gonna hit it, but we do what we can.

 

[zeejet]

Another tip to help prevent it in the future - don't water the foliage when you water your chinese elms. Obviously the rain is gonna hit it, but we do what we can.

Thanks for the reminder - I typically do not water foliage as that's been a general tip I've been receiving for other things. It's also not that humid in San Diego, but we do get dew condensation from temperature swings at dawn. It's also possible that the fungus was dormant on both trees when received and now coming alive.